1. Field of the Invention
The present invention relates to signal adapters and more particularly, to a signal adapter box for use with RJ-type transmission cables to extend the signal transmission distance between a HDMI signal source and a video output device.
2. Description of the Related Art
Following fast development of high technology, improved quality of electronic products have been continuously created and have appeared on the market. From early black and white TVs to later color picture tube TVs and the current plasma and LCD TVs, we see a great improvement in picture quality. An advanced plasma or LCD TV provides outstanding sharpness and high contrast for displaying high quality images. However, TV programs may not satisfy all people. Ampex introduced the Ampex VRX-1000, the first commercially successful videotape recorder, in 1956. In late 1970s, European and Japanese companies developed more technically advanced machines with more accurate electronic timers and greater tape duration, that the VCR started to become a mass market consumer product. In 1993, the VCD standard was created. In the late 1990s and early 2000s, DVD gradually overtook VHS as the most popular format for playback of prerecorded video.
VCD/DVD players must use a transmission cable to transmit signal to a TV for display. Earlierly, transmission cables of the video interface standard of DVI (Digital Video Interface) are used to maximize the visual quality of digital display devices such as flat panel LCD computer displays and digital projectors. Further, Intel i750 VLSI is the common choice for image compression and decompression. However, because DVI standard is simply for transmission of images but not for voice, an extra audio signal line is necessary. In view of this drawback, the compact audio/video connector interface of HDMI (High Definition Multimedia Interface) was developed for transmitting uncompressed digital streams. HDMI is backward-compatible with the single-link DVI carrying digital video used on modern computer monitors and graphics cards. In 2002, Intel developed HDCP (High-bandwidth Digital Content Protection) to control digital audio and video content as it travels across DVI (Digital Video Interface), HDMI (High Definition Multimedia Interface), or UDI (United Display Interface) connections. HDMI supports digital video formats of SXGA, UXGA, SDTV and HDTV as well as digital audio formats of CD, DVD-Audio and Dolby Digital/DTS. It also supports up to 165 Mpixel/s video (1080p60 Hz or UXGA) and 8-channel/192 kHz/24-bit audio and 48-bit xvYCC with Deep Color or over one billion colors with maximum bandwidth speed 5 Gbps.
The present time is the age of information explosion. Many exhibitions, conferences and other activities are performed daily in different places to introduce new products or designs to the public. In these places, audio output devices and/or big scale display screens are used for audio and video outputs to call people' attention. For the transmission of a video signal from a signal source to a display screen, a HDMI cable is usually used to assure video display quality. However, a HDMI cable has its transmission limitation. When the transmission distance surpasses 10 meters, the problem of signal attenuation will occur. Therefore, the location of the display screen must be limited to a range within 10 meters from the signal source.